Method and apparatus for providing an adaptable security level in an electronic communication

ABSTRACT

A method of communicating in a secure communication system, comprises the steps of assembling a message at a sender, then determining a security level, and including an indication of the security level in a header of the message. The message is then sent to a recipient.

This application claims priority from U.S. Provisional Patent Application No. 60/484,656 filed on Jul. 7, 2003

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for providing an adaptable security level in an electronic communication.

2. Description of the Prior Art

In electronic communications, it is often necessary to prevent an eavesdropper from intercepting message. It is also desirable to have an indication of the authenticity of a message, that is a verifiable identification of the sender. These goals are usually achieved through the use of cryptography. Private key cryptography requires sharing a secret key prior to initiating communications. Public key cryptography is generally preferred as it does not require such a shared secret key. Instead, each correspondent has a key pair including a private key and a public key. The public key may be provided by any convenient means, and does not need to be kept secret.

There are many variations in cryptographic algorithms, and various parameters that determine the precise implementation. In standards for wireless communications it has been customary to set these parameters in advance for each frame type. However, this approach limits the flexibility of the parameters.

When one device is communicating with several other devices, it will often need to establish separate parameters for each communication.

It is an object of the present invention to obviate or mitigate the above disadvantages.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a method of communicating in a secure communication system, comprising the steps of assembling as message at a sender, then determining a security level, and including an indication of the security level in a header of the message. The message is then sent to a recipient.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the preferred embodiments of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein:

FIG. 1 is a schematic representation of a communication system;

FIG. 2 is a schematic representation of an information frame exchanged in the communication system of FIG. 1;

FIG. 3 is a schematic representation of a frame control portion of the frame of FIG. 2;

FIG. 4 is a schematic representation of a method performed by a sender in FIG. 1;

FIG. 5 is a schematic representation of a method performed by a recipient in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a communication system 10 includes a pair of correspondents 12, 14 connected by a communication link 16. Each correspondent 12, 14 includes a respective cryptographic unit 18, 20.

Each correspondent 12, 14 can include a processor 22, 24. Each processor may be coupled to a display and to user input devices, such as a keyboard, mouse, or other suitable devices. If the display is touch sensitive, then the display itself can be employed as the user input device. A computer readable storage medium is coupled to each processor 22, 24 for providing instructions to the processor 22, 24 to instruct and/or configure processor 22, 24 to perform steps or algorithms related to the operation of each correspondent 12, 14, as further explained below. The computer readable medium can include hardware and/or software such as, by way of example only, magnetic disks, magnetic tape, optically readable medium such as CD ROM's, and semi-conductor memory such as PCMCIA cards. In each case, the medium may take the form of a portable item such as a small disk, floppy diskette, cassette, or it may take the form of a relatively large or immobile item such as hard disk drive, solid state memory card, or RAM provided in a support system. It should be noted that the above listed example mediums can be used either alone or in combination.

In order to transfer data between the correspondents 12, 14, a packet stream 30 is assembled at one of the correspondents in accordance with a defined protocol. The packet stream 30 is shown schematically in FIG. 2 and is composed of one or more frames 31, each of which has a header 32 and data 34. In some protocols, the packet may itself be organised as a frame with a header 32 a and the data 34 a consisting of a collection of individual frames. The header 32 is made up of a string of bits and contains control information at specified locations within the bit stream.

Included in each of the headers 34 are security control bits 33, that included a security mode bit 35 and integrity level bits 36, 37.

In this embodiment, security bit mode 35 is used to indicate whether encryption is on or off. Security bits 36 and 37 together are used to indicate which of four integrity levels, such as 0, 32, 64, or 128 bit key size is utilised. The security mode bit may be used to indicate alternative modes of operation, such as, authentication and the number of bits may be increased to accommodate different combinations. It will be recognized that providing security bits in each frame 31 of the stream 30 allows the security level to be on a frame-by-frame basis rather than on the basis of a pair of correspondents, therefore providing greater flexibility in organizing communications.

In order to provide security, certain minimum security levels may be used. These levels should be decided upon among all of the correspondents through an agreed-upon rule. This rule may be either static or dynamic.

In operation, the correspondent 12 performs the steps shown in FIG. 4 by the numeral 100 to send information to the correspondent 14. First, the correspondent 12 prepares data and a header at step 102. Then it selects the security level at step 104. The security level is determined by considering the minimum security level required by the recipient, the nature of the recipient, and the kind of data being transmitted. If the security level includes encryption, then the correspondent 12 encrypts the data at step 106. If the security level includes authentication, then the correspondent 12 signs the data at step 108. Then the correspondent 12 includes bits indicating the security mode and security level in the frame control at step 110. The correspondent 12 then sends the frame to the correspondent 14.

Upon receiving the frame, the correspondent 14 performs the steps shown in FIG. 5 by the numeral 120. The correspondent 14 first receives the frame at step 122. It then extracts the security bits at step 124. If the mode security bits 34 indicate encryption, then the correspondent 14 decrypts the data at step 126. If the security bits indicate authentication, then the correspondent 14 verifies the signature at step 126. Finally, the correspondent 14 checks the security level to ensure it meets predetermined minimum requirements. If either the encryption or authentication fails, or if the security level does not meet the minimum requirements, then the correspondent 14 rejects the message.

It will be recognized that providing security bits and an adjustable security level provides flexibility in protecting each frame of the communication. It is therefore possible for the sender to decide which frames should be encrypted but not authenticated. Since authentication typically increases the length of a message, this provides a savings in constrained environments when bandwidth is at a premium.

In a further embodiment, the correspondent 12 wishes to send the same message to multiple recipients 14 with varying minimum security requirements. In this case, the correspondent 12 chooses a security level high enough to meet all of the requirements. The correspondent 12 then proceeds as in FIG. 4 to assemble and send a message with the security level. The message will be accepted by each recipient since it meets each of their minimum requirements. It will be recognized that this embodiment provides greater efficiency than separately dealing with each recipient's requirements.

In another, embodiment, a different number of security bits are used. The actual number of bits is not limited to any one value, but rather may be predetermined for any given application. The security bits should indicate the algorithm parameters. They may be used to determine the length of a key as 40 bits or 128 bits, the version of a key to be used, or any other parameters of the encryption system.

Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto. 

1. A method of communicating between a pair of correspondent in a data communication system comprising the steps of assembly a data stream at one of said correspondents having at least one frame having a header and data, incorporating in said frame and indication of a security level associated with said frame, and forwarding said data stream to said other correspondent.
 2. A method according to claim 1 including the step of including an indication of a mode of security operation is said header.
 3. A method according to claim 1 including the step of including an indication of key size in said header.
 4. A method according to claim 1 including the step of determining a minimum security level to satisfy all of the recipients including an indication of such security level in said header.
 5. A method according to claim I wherein a recipient of said data stream examines said indication of security level and rejects said frame if it does not attain a minimum level.
 6. A method according to claim 2 wherein said mode of security operation includes encryption of said data.
 7. A method according to claim 2 wherein said mode of operation includes signing of said data.
 8. A method of communicating in a secure communication system, wherein each communication is divided into a plurality of frames, and each frame includes an indication of a security level, thereby allowing each frame to have a different security level to adapt to the nature of each frame.
 9. A method according to claim 8 wherein said indication of security level includes an indication of mode of operation and an indication of key size.
 10. A method according to claim 8 wherein said indication is selected based upon the content of data in said frame. 